Proton Density-weighted Sequences Research Articles

Comparison of MRI graded cartilage and MRI based volume measurement in knee osteoarthritis.

The aim of this study was to investigate the relationship between the femoral, tibial and patellar cartilage volume and MRI grading of the articular cartilage in patients with knee OA. Articular cartilage volumes of 65 postmenopausal women were determined by processing images acquired in the sagittal plane using a fast spin echo proton density-weighted sequence. The articular cartilages were divided into 5 compartments including lateral and medial tibial, lateral and medial femoral and patellar compartments. The articular cartilages were graded using a modified Outerbridge classification. Grade 0 indicated intact cartilage, grade 1 chondral softening with normal contour, grade 2 superficial fraying, grade 3 surface irregularity and thinning and grade 4 full thickness cartilage loss. The grades of articular cartilage were compared with cartilage volume measurements. In medial femoral cartilage, grade 1 had more volume compared to grade 0 cartilage (p: 0.017). In medial tibial cartilage, grade 1 had more volume compared to grade 0 and grade 2 cartilage (p: 0.045 and p: 0.027, respectively). In patellar cartilage, grade 1 cartilage had significantly more volume than grade 0 cartilage (p: 0.007). In lateral tibial and femoral cartilages, no significant difference was observed between grade 0 and grade 1 cartilage. Cartilage volume correlates well with MR grading of articular cartilage. The higher the grade of the cartilage the less the volume, with the exception of grade 1 lesions. Grade 1, reflects oedema in the cartilage and has a conflicting effect on volume measurement. The combination of MRI based volume measurement and grading of articular cartilage may provide an accurate method for the non-invasive evaluation and follow-up of articular cartilage.

Fast Fluid-Attenuated Inversion-Recovery MR of Intracranial Infections

PURPOSE To assess the usefulness of fast fluid-attenuated inversion-recovery (FLAIR) MR sequences in the diagnosis of intracranial infectious diseases. METHODS We compared fast FLAIR images with conventional spin-echo images (T1- and T2-weighted) obtained in 20 patients with infectious diseases (six with encephalitis, five with brain abscesses, three with meningitis, two with meningoencephalitis, two with Creutzfeldt-Jakob disease, one with epidural empyema, and one with cysticercosis). Two neuroradiologists independently reviewed the FLAIR images and compared them with the conventional spin-echo images, obtaining agreement in all patients. RESULTS FLAIR images of diagnostic quality were obtained in 18 patients. In two patients, FLAIR images were degraded by motion. Lesions in the patients with encephalitis and meningoencephalitis were better delineated on FLAIR images than on spin-echo images. FLAIR images clearly depicted lesions in the basal ganglia in both patients with Creutzfeldt-Jakob disease. In patients with brain abscess, meningitis, cysticercosis, and epidural empyema, FLAIR images provided no more information than conventional spin-echo images, and the lesions were seen better on postcontrast T1-weighted spin-echo images. CONCLUSION Fast FLAIR images showed pathologic changes in intracranial infectious diseases better than or as well as conventional T2- and proton density-weighted spin-echo sequences. However, postcontrast T1-weighted spin-echo sequences resulted in better visibility of abscess, meningitis, cysticercosis, and epidural empyema than did FLAIR images.

The effect of using shorter echo times in MR imaging of knee menisci: a study using a porcine model.

Increasingly shorter TEs are being used for T1-weighted and proton density-weighted sequences in MR imaging of the knee. This study aims to evaluate the effect of a short TE on meniscal signal intensity. Thirty porcine knees were imaged with a 1.5-T MR scanner using spin-echo T1-weighted and proton density-weighted sequences. TR was kept constant at 700 msec for T1-weighted and 2200 msec for proton density-weighted sequences. For each set of sequences, sagittal images were obtained using these TE values: 9, 12, 16, 20, and 25 msec. Imaging parameters, such as slice thickness and interslice gap, number of excitations, matrix size, and field of view, were identical for each set of sequences. Using a fixed window level and width, we assessed the anterior and posterior horns of the medial meniscus for signal hyperintensity at each TE value. Signal intensity was also measured in eight knees. The menisci were then dissected and examined grossly and histopathologically. Intrameniscal signal intensity increased progressively with shorter TEs. At a TE of 9 msec, signal hyperintensity was present in 100% of T1-weighted and 96.7% of proton density-weighted images. At a TE of 12 msec, signal hyperintensity was seen in 86.7% of T1-weighted and 80% of proton density-weighted images. At a TE of 16 msec, increased signal intensity was seen in only 3.3% of T1-weighted and 6.6% of proton density-weighted images. At TEs of 20 and 25 msec, increased signal intensity was seen in none of the T1-weighted and proton density-weighted images. Meniscal signal intensity increased exponentially at very short TE values. All menisci were found to be normal on gross and histopathological examination. Spurious signal hyperintensity appears in normal menisci at short TE values. Images acquired with short TEs should be interpreted with caution, and a TE of 16 msec or more is recommended.